Field of the Disclosure
The present disclosure relates to a numerical control (NC) program generating apparatus which generates, for an NC machine tool including a plurality of operation units each having a power source, an NC program for controlling the operation units and which is capable of saving power.
Background of the Disclosure
Operation control methods and numerical control methods are known that attempt to save power during use of a machine tool.
For example, Japanese Unexamined Patent Application Publication No. 2001-277071 (“the JP '071 publication”) discloses an operation control method in which, when operation of the machine tool cannot be continued due to the presence of incorrect syntax or an incorrect command code description in a command in a machining program or due to the occurrence of abnormality in a controller or the machine tool and this brings the machine tool into a machining interrupted state or a suspended state, rotation of a spindle is stopped and operation of supplementary equipment such as a coolant supply system and the like is stopped.
It is noted that the determination of whether or not the machine tool is in a machining interrupted state or a suspended state is made by monitoring a control command state and an operation state of the machine tool in the state where the machine tool is set to an automatic operation mode, and the machine tool is determined to be in a machining interrupted state or a suspended state in each of the following cases: a) the case where, during the machine tool being in the automatic operation mode, there is no movement command and no interrupt operation is performed; b) the case where, during the machine tool being in the automatic operation mode, a speed command is zero in the middle of a movement command; and c) the case where, during the machine tool being in the automatic operation mode, there is no movement command and there is no interrupt movement command in the middle of an interrupt operation.
According to the operation control method described in the JP '071 publication, in the case where the machine tool is brought into a machining interrupted state or a suspended state, power saving processing, such as stopping rotation of a spindle, stopping operation of a coolant supply unit, and stopping operation of a chip discharge conveyor, is executed; therefore unnecessary power consumption during the machine tool being in a machining interrupted state or a suspended state is prevented, thereby saving power.
Further, a numerical control method is disclosed in Japanese Unexamined Patent Application Publication No. 2011-118952 (“the JP '952 publication”) that is used when rotating a spindle. In the method, a machining program is analyzed by reading at least one block ahead and, based on the results of the pre-reading analysis, an execution time until cutting feed is started after a spindle rotation command is made and a spindle acceleration time until the number of times of spindle rotation reaches the number of times following the spindle rotation command after starting the spindle are calculated, and when the elapsed time after the spindle rotation command was made exceeds a time obtained by subtracting the spindle acceleration time from the execution time, the spindle is started.
Further, the JP '952 publication discloses a numerical control method for stopping the spindle in the middle of a spindle rotation command, and in the method, a machining program is analyzed by reading at least one block ahead. In the case where, as a result of the read-ahead analysis, it is in the middle of a spindle rotation command and there is a non-cutting block, a spindle stop time from the non-cutting block to start of cutting feed and a spindle acceleration/deceleration time are calculated based on the results of the read-ahead analysis, and when the spindle stop time is longer than the spindle acceleration/deceleration time, rotation of the spindle is stopped.
According to the numerical control methods disclosed in the JP '952 publication, taking the spindle acceleration time into consideration, start of the spindle can be delayed until just before start of cutting feed; therefore, the power required for rotation of the spindle can be reduced and saved as much as the delay. Further, when there is a non-cutting block, rotation of the spindle is stopped taking the spindle acceleration/deceleration time into consideration; therefore, the power required for rotation of the spindle can be reduced and saved as much as the amount related to the stop of the spindle.